1. Field of the Invention
The present invention relates to an image processing method and apparatus, for reading and editing the document image, and more particularly to a method and apparatus for effecting a specified type of image processing for different indicated regions in the document image.
2. Description of the Prior Art
A conventional processor normally comprises an image input unit and image output unit, such as a laser printer. The image input unit reads a document image and converts the image to an electric signal. Then, the electric image signal is subjected to various image processings. The image output unit transforms the electric image signal back into the document image.
Japanese Laid-Open Publications 60-242480 and 60-213168 disclose such an image processor wherein the document image is subjected to a partial region indication image processing, and is processed thereby differing from other region. Use of such a processor, in a copying machine, for example, subjects only the image in the indicated region to editing, such as deletion, extraction, color conversion, or back-screening.
In the prior art, to indicate a closed region to be edited, the x-y coordinates data of the region in the document image are inputted to the image processor, typically through numeral keys or a digitizer. The indication is often made by defining the coordinates of two vertices, for example, of a rectangle on a diagonal line thereof or of many points in the region of a polygon.
However, such indication has an inherent drawback in that they can not accurately indicate the region to be indicated, unless the region has a simple shape such a rectangle. For example, it would be difficult to accurately indicate a fan-shaped portion of a circular graph shown in FIG. 5. The fan-shaped portion designated with a mark "*" shown in FIG. 5(a), is rendered to processing to yield a copied image shown in FIG. 5(b). To do it in a prior art method, the coordinates of a sufficient number of sampling points for the contour or outlne of the fan-shaped portion of the circular graph to be defined, to accurately indicate the closed region to be indicated, requiring much labor. Reducing the number of sampling points will increase chances for an erroneous indication of the closed region. Furthermore, when an operator inputs the coordinates of the closed region to be indicated in the document, discrepancies between the position of the image actually read by the image input unit and the coordinates the operator inputs may occur due to mechanical and positional errors caused by erroneous positioning of the document.